Bardet-Biedl syndrome (BBS) |

Bardet-Biedl syndrome (BBS)

Bardet-Biedl syndrome (BBS) is named after the French physician G. Bardet and Czechoslovakian pathologist and endocrinologist A. Biedl who first described this genetic disorder. BBS is a rare ciliopathy in humans occurring with a prevalence of 1:70,000 live births.
BBS is a heterogenous pleiotropic disorder inherited in a mainly recessive manner. Two forms (BBS1, BBS2) have been identified. Clinical features include retinal degeneration, cognitive impairment, obesity, renal cystic disease, polydactyly and occasionally situs inversus.

Twelve genes (BBS1-12) in total are known to be implicated in its causation. The gene products encoded by these BBS genes, named BBS proteins, are localized to the cilium/basal body/centrosome complex of the cell. When mutated, BBS genes affect normal cilia functions, which, in turn, cause BBS. The detailed biochemical mechanism that leads to BBS remains unclear.

Figure 1. (A) Braquidactyly and postaxial polydactyly of hands. (B) Braquidactyly and postaxial polydactyly of feet.
[Taken from Ventura MP, Vianna RNG, Solari, HP, Filho JPS, Burnier MN Jr (2006). Bardetâ€“Biedl syndrome associated with glaucoma. Eye 20: 114-116].

Figure 2. Fundus of a 31 year-old patient with Bardet Biedl syndrome. The peripheral retina does not show any large lesion but the macula is atrophic.
[Taken from Hamel CP (2007). Cone rod dystrophies. Orphanet J Rare Dis 2: 7].